[EM] SFC and Conodrcet "full support of A>B and B>C at same time"
Warren Smith
wds at math.temple.edu
Sun Feb 11 13:39:04 PST 2007
Ossipoff: But if Warren has a quibble about what it means to fully vote X over Y, then
I refer him to my criteria SFC, GSFC, and SDSC.
--WDS: here is the definition of SFC given by Ossipoff (CW=Condorcet winner):
"SFC: If no one falsifies a preference, and there's a CW, and a majority of all the voters
prefer the CW to candidate Y, and vote sincerely, then Y shouldn't win."
Ossipoff: "[SFC] is met by SSD and other good wv Condorcet versions."
Ossipoff: "I call [SFC] the pinnacle of the promise of rank-balloting."
However, Ossipoff is wrong. Here is a counterexample. There are 3 voters:
A>B>C
B>C>A
C>A>B *
where the * vote is insincere. The unstarred two voters are a "majority"
who prefer the sincere-CW (who is B) over C, and who vote sincerely. But the total vote
is a 3-way perfect tie. Therefore C can win. But according to Ossipoff's SFC, C cannot
win. This counterexample works against every Condorcet method satisfying anonymity.
Therefore:
Theorem: no Condorcet method satisfying anonymity satisfies Ossipoff's
SFC criterion.
Perhaps we can salvage Ossipoff by figuring by "CW" he meant "the CW based on
the votes as cast whether sincere or not. In that case, however,
the words "If no one falsifies a preference" and the words
"and a majority of all the voters prefer the CW to candidate Y, and vote sincerely,"
all become unnecessary and SFC simply becomes equivalent to having a Condorcet method.
In that case Ossipoff would be asserting that good Condorcet methods are Condorcet methods.
--WDS continues:
Ossipoff contends that Condorcet participation failure is a mere "embarrassment" and
does not affect his "obvious" claim that with Condorcet methods, a voter can fully support A>B
and B>C at the same time, unlike in range voting. Well, I will not debate
the meaning of subjective terms such as embarrassment. I have instead refuted Ossipoff's
objectively defined alleged theorem. Also, I quote my own web page
http://rangevoting.org/OssiDelusion.html
--begin quote
I do not see how you, by (say) casting the vote Nader>Gore>Bush, causing Nader to lose when he
otherwise would have won, would be "fully supporting" Nader! (Incidentally, in range voting,
this paradox never arises: your vote A>everybody can never cause A's defeat, and your vote
saying everybody>B can never cause B to rise above bottom.) So I think Ossipoff's
appealing point here, is actually an appealing delusion.
If you disagree, then consider the following "voting method":
a. you supply rank-order ballots,
b. I ignore them and choose whoever I want to be the winner.
As far as I can tell, you, by disagreeing, presumably feel that this method also has the
property that a voter can "fully support A>B and B>C at the same time"??
In my view, it shouldn't be about some bogus perception of "full support." It should be about
real support, which means, helping A win or at least not causing A's loss. If your vote
doesn't help A win (and in fact causes A to lose) then it was not "fully supporting" A .
With that definition: no Condorcet method always allows a voter to fully
support A>B and B>C at the same time.
--end quote
Finally, to refute one more misleading Ossipoff statement.
In reply to
WDS: I suspect that in every Condorcet system,
whether rank-equalities are allowed or not, and whether "winning-votes" are used or
not, there are election situations where you (a voter or co-feeling small bloc
of voters) must cast a vote which
is fully-dishonest about one or more orderings, i.e in which you say A>B
when you honestly feel B>A. If you do not do this in your vote,
then you get a worse election winner.
Ossipoff reply: I have a big surprise for Warren: I've been pointing out for a long time
that Condorcet wv doesn't strictly meet FBC.
--WDS: While that is nice. A re-examination of my quote indicates that I was not
talking about FBC. I was talking about order-reversal in votes. The two are different
since it is possible to betray a favorite without reversing any order.
Ossipoff then makes various false implications about what I think,
like how "surprised" I am, etc etc,
all of which are purely present in his own mind, then he proceeds to attack his own mind.
Warren D Smith
http://rangevoting.org
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